Flooring system including a dry glue

ABSTRACT

A flooring system includes a plurality of tongue-and-groove panels, and a preglue. When activated, the preglue has a tensile strength of 7-20 kN/m when measured with a gap less than 0.1 mm and a pull rate of 2 mm/min; a storage stability of at least one year; a low initial tack value; and a set time of at least 45 minutes; as well as a creep strength of between 7 and 20 kN/m, when measured with a gap less than 0.1 mm and a pull rate of 0.02 mm/min.

CROSS REFERENCE TO RELATED APPLICATIONS

This PCT application claims priority from U.S. Provisional ApplicationNo. 60/701,486, filed Jul. 22, 2005.

BACKGROUND

1. Field of the Invention

The invention is a flooring system, utilizing a number of flooringelements, and a “dry” (to the touch) glue for maintaining a tight jointbetween the flooring elements.

2. Background of the Invention

Wood or laminate flooring has become increasingly popular. As such, manydifferent types of this flooring have been developed. Generally, thistype of flooring is assembled by providing a plurality of similarpanels, which are interfit or otherwise secured together and which“float” above the subfloor, i.e., the flooring is not mechanicallyattached to the subfloor.

In conventional hardwood or other flooring systems, edges of rectangularboards or planks are often provided with a tongue-and-groove joiningsystem, whereby a first plank has on at least one edge, a protrudingtongue, and a second plank, to be installed adjacent and abutting thefirst plank, has, on at least one side, a groove, which correspondssubstantially to the size and shape of the tongue. Thus, in order toinstall the first board adjacent to the second board, the tongue isinserted into the groove. In some systems, the tongue and groove form alock, hindering or preventing separation of the boards.

Such conventional tongue-and-groove systems are generally installed byrelatively moving one panel with respect to the second panel. Forexample, U.S. Pat. Nos. 6,421,970 and 6,823,638 teach a system wherebythe boards are moved relatively horizontally. U.S. Pat. Nos. 6,591,568and 6,647,690 teach systems whereby assembly can be completed byrotating and/or through a vertical movement. Other examples oftongue-and-groove systems are disclosed by U.S. Pat. Nos. 6,786,019;6,006,486; 6,862,857; 6,711,869; 6,536,178 (relative vertical movement);U.S. Pat. No. 6,601,359 (relative horizontal or rotational movement);and U.S. Pat. No. 6,865,855. The resulting joint may also have fittingclearances for the drainage of adhesive, if any, such as described byU.S. Pat. No. 6,682,254. Additional components, such as joiningprofiles, guiding means or resilient members may also be used, forexample as taught by U.S. Pat. Nos. 6,729,091; 6,763,643; 6,966,161;6,920,732; and 6,854,235. Each of the references mentioned in thisparagraph is expressly incorporated by reference in its entirety.

Additionally, the size and shape of the tongues and grooves variesgreatly. For example, U.S. Pat. No. 6,823,638 (herein incorporated byreference in its entirety) teaches a tongue with a groove providedtherein and a corresponding groove with a tongue provided therein.

Typical flooring elements used in accordance with the present inventionare laminate flooring elements, including a core, a decorative surface,and a wear layer. Typical cores include wood, fiberboard, such as highdensity fiberboard (HDF) or medium density fiberboard (MDF), gypsum,high-density reinforced plaster, plywood, oriented strand board (OSB),cork, bamboo, flaxboard, plastics (e.g., extrudable and/or moldablethermosetting and thermoplastic resins, the latter including highdensity olefins and PVC), or other structural material, such as metals(e.g., aluminum, copper, brass, alloys thereof and stainless steel) orcomposites.

Such laminate flooring elements generally include a decorative surface.Typical decorative surfaces are formed from one or more patterned papersheets, impregnated with a resin, and placed atop the core. Manyelements also are provided with a surface texture which coincides withthe pattern or design of the paper sheets, in order to enhance therealism thereof, as described by U.S. Pat. No. 7,003,364 (hereinincorporated by reference in its entirety). However, such decorativesurface can be provided by printing directly, on the core material. Theuppermost surface of the element most often includes a wear layer,formed by a resinous layer including hard particles to impart resistanceagainst scratching, abrasion, and denting. Such particles are,typically, diamond, silicon carbide, alumina (e.g., alpha-alumina), orceramics, which can have a Mohs' hardness of at least 6.0.

However, in many of these systems, especially floating floors, anadhesive or glue is often used, such that the assembled panels do notseparate. Most often, the glue must be separately purchased, andseparately applied in a step immediately preceding joining of thepanels.

Although flooring systems have been commercialized with a “preglue,”wherein the glue or other adhesive is applied at the factory, suchsystems have drawbacks, and have heretofore required an additional step.Such additional steps typically include application of an external agent(e.g., water or other chemical activating agent, and ultrasonicwaves—either immediately before or following installation), or removalof a protective strip, in order to render the preglue in its activestate.

SUMMARY OF THE INVENTION

Thus, the present inventors have developed a flooring system using a“dry” preglue system, which preglue is applied at the factory, whichdoes not require a separate application of an external agent or removalof a protective strip, and/or which additionally provides adhesiveproperties not found in any commercial system.

In one embodiment, the adhesive or components of the adhesive whichreact with one more other components can be contained in small“microcapsules,” which, under pressure and/or shear, can be ruptured toallow the glue to adhere to the panels. Examples of “microcapsules” aredisclosed in U.S. Publication No. 2002-0127374 (herein incorporated byreference in its entirety), and may be organic or inorganic.

According to the invention, upon assembly of the panels, and mating ofthe tongue and groove, the adhesive becomes operative to prevent thepanels from separating, by even a small amount. This can be accomplishedby rupturing one or more containers, such as the aforementionedmicrocapsules, containing the glue or precursors thereof. Suchcontainers may also be in the form of one or more tubes containing,e.g., the adhesive material (such as in an encapsulated form therein),separated activators and/or precursors, or two-part systems. Such tubescan be segmented with seals therebetween, such a described by U.S. Pat.No. 7,029,741, herein incorporated by reference in its entirety.

In a preferred embodiment, the adhesive, once activated and finally set,will exhibit particular properties. For example, the followingproperties are preferred:

Property Value Creep Strength Greater than 10 kN/m Tensile Strength10-15 kN/m Storage Stability Greater than one year Hazardous MaterialsNone Initial Tack Low Set Time 10-15 mins Odor Little or none CuringTime Within 24 hours

In one embodiment, the adhesive, or components thereof, is applied tothe entire surface of each of the tongue and groove, but more typically,the adhesive is strategically placed in select locations on the tongueand/or inside the groove. By selecting these application locations, theeffectiveness of the adhesive can be maximized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustrating an embodiment of the inventionshowing a first-part curative and second-part curative.

FIG. 2 is a cutaway perspective view of a substrate having coatingsapplied according to an embodiment of the invention.

FIG. 3 is a side view of an alternative embodiment depictingencapsulated activator showing the second-part curative where catalystis applied as a lower layer, and where activator is separatelymicroencapsulated.

FIG. 4 is an alternative embodiment depicting the second-part curativewhere activator is a lower layer and catalyst is the middle layer or isin a middle layer.

FIG. 5 is an embodiment depicting the second-part curative disposed onopposite sides of the layer with the microcapsules containing monomerand the first-part curative.

FIG. 6 illustrates alternate embodiments where the components of thesystem are coated onto separate surfaces. In version A the capsules withfirst-part curative are applied to the same surface with catalyst. Inversion B the catalyst is applied to the surface coated with a secondpopulation of capsules encapsulating activator.

FIGS. 6 and 7 show a tongue-and-groove system which may be used with thepreglue in accordance with the invention.

FIG. 8 shows the tongue-and-groove system of FIG. 6 in its assembledcondition.

FIG. 9 shows a second tongue-and-groove system which may be used inaccordance with the invention.

FIG. 10 shows an additional tongue-and-groove system which may be usedwith the preglue in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Initially, as used throughout the specification and claims, the terms“plank,” board,” and “tiles” mean any type of surface covering materialand in any shape. For example, the planks, boards and tiles may be partof a flooring, wall covering, desk, countertop, cabinet, door, vehicleor ceiling component, and can be rectangular, square or have the shapeof any other polygon. Although the glue of the invention is particularlydesigned to be used with laminate flooring materials, the terms “plank,”“board” and “tile” are not so limited. For example, board can convey anytype of flooring material, including, plastic, composite materials,hardwood, flaxboard, high density fiber-reinforced plaster, extrudedwood, engineered wood, and even ceramic and other non-cellulosicmaterials. Additionally, the planks may have a decorative upper surface,formed from a material different from that of the remainder of theplank. Typical materials include, laminates (such as foils, plasticsheets, and ceramics (e.g., individual tiles)).

Similarly, the term “preglue,” “glue” and “adhesive” as used in thespecification and claims, means a substance which can chemically orphysically join two, at least tangentially, adjacent surfaces to securethe surfaces together. In some cases, such a substance can be appliedduring manufacture of the panels. That is to say, before the panelsleave the factory, the glue is applied, thus eliminating the need toprovide a separate adhesive material just before assembly. Typically,the glue is applied in a non-activated state, such that some later eventis needed to convert the preglue into its adhesive state. This inventionis particularly directed to a dry preglue, i.e., a glue which is appliedat the factory, but does not need the application of an externalactivator to cause the adhesive effect. Such adhesive effect ifpreferably achieved by breaking or rupturing a film, such as the wall ofa microcapsule or segmented tube. It is additionally considered withinthe scope of the invention to apply the glue in an activated state, buthave a suppressing agent applied thereto, such that the glue has been“de-activated,” awaiting “re-activation” at a later time.

FIG. 7 shows a typical tongue-and-groove system which is designed to beassembled horizontally with which the dry preglue of the invention maybe used. A first panel 110 is provided with a tongue 112. The tongue 112is provided with a retaining element 114, and a distal surface 116, aswell as an upper surface 118 and a lower surface 120. Additionally, asshown in FIG. 7, the first panel 110 includes a nose 122, designed toabut an adjacent panel when assembled to form a solid, gap-free surface.

A second panel 140 is provided with a groove 141, a cooperatingretaining element 142, and a proximal surface 144, as well as upper andlower surfaces, 146 and 148 respectively, and a distal upper surface150.

Although the retaining elements 114 and 142 are shown as being of aparticular construction and at a particular location, such aconfiguration is shown for convenience only. In other words, the size,shape, type and/or location of the retaining elements 114 and 142 may bealtered in any manner without departing from the invention. Thus, thepreglue of the invention may be used on any type of tongue-and-groovesystem known in the art, such as those disclosed in, but not limited tothose of, U.S. Pat. No. 6,421,970, No. 6,591,568, No. 6,647,690, and No.5,823,638 (each of which is hereby incorporated by reference in itsentirety). Similarly, there may be multiple retaining elements 114, 142.Moreover, it should be understood that the first panel 110 may be joinedto the second panel 140 by, for example, relative horizontal movement,and to a third panel 160 (not shown) by an alternative method, e.g., byrelative vertical or rotational movement.

Similarly, as the invention utilizes an adhesive material, it isconsidered within the scope of the invention to eliminate the retainingelements 114 and 142 entirely, thus relying totally upon the adhesivestrength of the preglue. Additionally, the retaining elements 114, 142need not be sufficient, alone, to hold the panels 110, 140 together whenunder normal use.

For example, as long as the retaining elements 114, 142 can maintain theposition of the panels 110, 140 in their installed positions for atleast a short period of time, the preglue of the invention can haveenough time to set, to maintain a secure connection, such as a tightjoint, of the panels 110, 140. In one embodiment, the locking elements114, 142 can be assembled by human manual pressure, i.e., human musclepower alone, without the need for additional mechanical tools, such as atapping block and hammer, as is commonly required to assemble lockingelements previously known in the art.

FIG. 8 shows the first panel 110 and the second panel 140 afterassembly. Specifically, the tongue 112 of the first panel 110 isinserted into the groove 141 of the second panel to secure the panels110, 140 together. When assembled, the panels 110, 140 meet at leastwhere the top surface 118 of the tongue 112 meets the upper surface 146,and where the lower surface of the tongue 120 meets the lower surface ofthe groove 148, as well as where the nose 122 meets the distal uppersurface 150. In a preferred embodiment, at each of these contactsurfaces 200 a-d, the preglue of the invention functions to hold thepanels 110, 140 together. However, it is within the scope of theinvention to apply the preglue to any number of the contact surfaces 200a-d, and in any combination.

In addition to the horizontally joined panels as shown in FIGS. 7 and 8,the invention is applicable to be used with any assembly method. Forexample, FIG. 9 depicts a typical tongue-and-groove system which isdesigned to be assembled vertically with which the preglue of theinvention, and FIG. 10 depicts a typical tongue-and-groove system whichmay be assembled through rotational movement with the preglue of theinvention.

In a preferred embodiment, the dry preglue exhibits specific properties.For example, the creep strength with a gap less than 0.10 mm and a pullrate of 0.02 mm/min is between 1 and 50 kN/m, typically 2-30 kN/m, moretypically 7-20 kN/m and preferably 10-15 kN/m. The creep strength cannever be too high, and the minimum value is based, in part, on what typeof flooring is used. For a typical laminate floor, formed from low orhigh pressure laminate with a traditional high or medium densityfibreboard core, a minimum value should be above 10 kN/m.

The creep strength is measured with a gap between the laminate edgesbeing less then 0.10 mm, at a strength of 10-15 kN/m. Normally suchjoint strength is measured at high piston rate, typically 2 mm/min.However, in an installed floor there are long term forces generated fromhumidity and temperature changes, and over time this can create gapsbetween the planks. The reason for applying the adhesive is to increasethe strength of the joint, so it can resist these long-term forces.Simulating such the slow forces was performed with a uniaxial machine,such as Lloyd LR50K testing machine (available from AMKTEK, Inc., ofLargo, Fla.) with an external extensometer, and the pieces were pulledapart with a joint opening rate of 0.02 mm/min. This pull rate is chosenfor practical reasons (it is possible to use other pull rates 0.001-1mm/min) and that it correlates with previous performed long-termstrength tests. In long term strength tests, identical test pieces arehanged with different weights. The weight is increased over time, untilthe test piece breaks. This could take several weeks.

The preglue of the invention also has a particular tensile strength. Forexample, the tensile strength with a gap less than 0.10 mm and a pullrate of 2 mm/min is between 1 and 50 kN/m, typically 2-30 kN/m, moretypically 7-20 kN/m and preferably 10-15 kN/m. The tensile strength ismeasured in the same way as the creep strength except for the pull rate(2 mm/min). Here, also the gap is important.

An important factor in the commercial viability of the preglue is thestorage stability after application on planks. In an embodiment, thepreglue can maintain its properties for at least 6 months, typicallygreater than 9 months, and preferably at least as long as one full year,when maintained at a temperature of between 10 and 150° F. (−12-66° C.),irrespective of the relative humidity. The adhesive typically meets thecreep strength requirement after one year of having been applied on theboard. Temperature and humidity are the important environmentalconditions. The capsules typically also withstand normal light, so it isnot necessary to pack the planks with special foil, and should alsowithstand exposure to oxygen and air without the need for any additionalmaterials, such as coatings or packaging.

Preferably only non-toxic materials are used. Such non-toxic materialsinclude those materials that are non-hazardous to humans and otheranimals (both to the skin and mucous membranes), and other, as may bedefined by the Occupational Safety & Health Administration of the UnitedStates Department of Labor.

As used herein, non-toxic may also include hypo-allergenic materials,i.e., materials which do not cause allergic reactions in humans. Thesematerials have little, if any, reaction, when they come in contact withhuman skin or otherwise contact the human body.

The preferred dry preglue has a low initial tack value, which results inlittle or no adhesion or attraction of dust and other particles. Bymaintaining a low initial tack value, any negative influence from thepresence of dust and other small particles can be significantly reducedif not eliminated. Initial tack, as used throughout this specificationand claims, means before the capsules are broken. Such tackiness can bemeasured via any method, but is typically measured visually. Theimportant thing is that no or little dust or particles adheres to theadhesive before the planks are assembled. The risks with adhesion ofdust are that it can be difficult to assemble the planks, create proudedges and the strength of the adhesive can be reduced.

In one embodiment, the dry preglue has little or no smell, either beforeor after activation. Such a condition will be tested at the SwedishNational Testing and Research Institute (SP). The important thing isthat there is no unpleasant smell from the adhesive during installationand after the installation. Smell is difficult to measure becausedifferent people react differently to smells. What SP will do is tomeasure the volatile components with a method called FLEC (field andlaboratory emission cell). The presence or absence of smell or odor canalso be measured by human observation. However, in other embodiments ofthe invention, the release or origination of organic or inorganicodiferous components (such as a mercaptan or other sulfur-containingcomponent) can alert the installer that the dry preglue has beenactivated. In such circumstances, odiferous substances can be readilyidentified in minute quantities, e.g., on the order of 100 ppm, 50 ppmor even as low as 10 ppm, could be released or generated.

Once the dry preglue has been activated, in preferred embodiments, theglue should not begin to set until the expiration of a predeterminedperiod of time. By providing a predetermined set time of, for example,as long as 45 minutes to one hour, the installer is given an opportunityto assemble the planks, and if needed, remove one or more withoutdestroying them. If, for example, one plank were damaged or was notcompletely interfit with the adjacent panels, the installer would beable to correct this problem. Practical set times can be between 1minute and 1 hour, typically between 10 and 45 minutes, and preferablybetween 10 and 15 minutes. Longer predetermined set times force theinstaller to avoid putting pressure on the joints until after the settime has expired, and shorter set times negate the ability todisassemble the boards without damage thereto.

Once the preglue begins to set, it should achieve its final properties,such as creep strength and tensile strength within a reasonable curingtime. Typical curing times can be as long as one week, but arepreferably less than 2 days, and most preferably less than 24 hours.

The preglue may be applied in any number of manners to the panels.Particular examples of the locations of which the glue may be appliedare taught by U.S. Published Application No. 2002-0189747 (incorporatedby reference in its entirety), wherein the adhesive is applied tosubstantially all of each surface of the tongue 112, other than thedistal surface 116, as well as to substantially all surfaces of thegroove 141, other than the proximal surface 144. Such capsules typicallyhave a diameter between 1 and 700 μm, more typically between 10 and 100μm, and preferably between 10 and 50 μm.

While it is preferred that the preglue system be spread across theentire length of the edge of the tongue and/or groove, it is consideredwithin the invention to apply the components on substantially less thanthe entire edge. For example, depending upon the type of locking elementbeing used, it may only be necessary to have the glue system on, 75%,50%, 25% or even 10% or less of the entire length of the edge.

In one embodiment, the preglue system requires (A) a monomer, (B) aninitiator, (C) an activator, and (D) a catalyst. In order for thepreglue to become fully activated, typically, it is necessary to reacteach of components (A)-(C) in the presence of (D). Thus, when the panelsof the invention leave the factory, at least one component is typicallyseparated from the remainder. Separating can be spatial or can involveisolation of one or more components, such as by microencapsulation.

Generally, the system additionally typically includes a binder. One ormore of the components, preferably the catalyst, may be contained in thebinder. Suitable binders are carriers or vehicles for the microcapsulesor non-encapsulated component and can include dried solvents. Examplesof binder materials include water-based adhesives or lacquers (e.g.,PVAc), solvent based adhesives or lacquers, UV-curing adhesives orlacquer, latex, starch, only solvent and only water.

Other optional components include a foaming agent, such as polyols andpolyethers with isocyanates which cause the glue to foam or bubble whenactivated. By utilizing such a foaming agent, the glue can expand involume to flow and fill interstices or spaces between the planks. Thisis especially desirable when it is desired to seal the space between theplanks immediately below the noses of the planks.

The monomer can be any material, which, when exposed one or more othercomponents forms a polymer which can join the boards of the invention.Typical monomers include acrylates, urethanes and epoxies and arepreferably 100% solidified and cured by the action of free radicals,cationic reactions and anionic reactions. The catalyst is typicallycopper, such as a copper solution, e.g., copper chloride in an acetonesolvent.

The initiator is typically a chemical added to help start the chemicalreaction such as polymerization, needed to activate or set the adhesive.Such polymerization may be cross-linking or chain extending. Its actionis typically similar to that of a catalyst, except that it is usuallyconsumed in the reaction. In polymer chemistry, an initiator is achemical compound that initiates a chain reaction. Typically thesecompounds decompose to form either radical, anionic, or cationicspecies, which in turn serve as a reactive center for the propagation ofchain polymerization. An example of a commonly used radical initiatorwould be tertiary-butyl hydroperoxide. This is a water soluble compoundthat, upon mild heating, breaks into two radical species. The initiatoris typically a peroxide, such as cumene hydroperoxide.

The activator is typically a chemical used to accelerate a reaction orincrease chemical activity in another material, for example, to activatethe initiator to begin the reaction. A generic example a suitableactivators are amines.

The adhesive system may be formulated as follows:

-   -   a. Capsule 1:        -   i. Monomers (tetrahydrofurfuryl methacrylate and butylene            glycol dimethacrylate) and        -   ii. Initiator (cumene hydroperoxide).    -   b. Capsule 2:        -   i. Activator (propyl dihydropyridine).    -   c. The binder contains the catalyst (copper dichloride        dihydrate).    -   d. When the capsules are broken, the activator activates the        initiator and then the initiator initiates the polymerization of        the monomers and the catalyst catalyzes the polymerization        reaction.

The various components, as well as binder therefor, can be applied in anumber of manners. Typical examples include, vacuum coating, spraying,rolling, brushing, dipping, and electrostatic spraying. When applied,the wet film thickness is typically less than 500 μm, more typicallyless than 200 μm, and preferably less than 100 μm. However, afteractivation, the thickness is typically less than 1000 μm, more typicallyless than 500 μm, and preferably less than 200 μm.

The wet film thickness should be less than 1000 μm and, more typicallybetween 300 and 600 μm. The dry film thickness should be less than 800μm and, typically less than 500 μm, and preferably between 150 and 300μm. However, after activation, the thickness is typically less than 500μm, more typically less than 200 μm, and preferably less than 100 μm.

It is possible to separate the components by applying the components toboth of the panels. However, in order to prevent mixing of thecomponents prematurely, at least one of the components must be separatedfrom the remainder. In one embodiment, components (B)-(D) are applied toone of the tongue or groove, and the monomer is applied to the other ofthe tongue and groove. Thus, when the tongue and groove are mated, themonomer can contact the activator, catalyst and initiator to activatethe glue. Similarly, the components may be separated in any manner, aslong as the activation can be prohibited until desired.

It is also possible to encapsulate one or more of the components. Forexample, instead of having one or more components, such as the monomer,separated from the remaining components by being located on a separatepanel, one or more components can be encapsulated to prevent mixinguntil desired. This encapsulation may be organic or inorganic, such asthat which is disclosed in U.S. Publication No. 2002-0127374, as well asone or more of melamine, urea and formaldehyde. The capsules, regardlessof their size, may also be formed from glass, polymer, gellable colloidsand other materials as hereinafter discussed, or another substantiallyrigid material. In these embodiments, pressure generated by physicallyjoining the boards causes the capsules to rupture.

In another embodiment, the capsules are broken by a chemical reaction.For example, the capsule can include a material which, when exposed to asolvent located on the opposite board, will rupture or otherwise open,allowing the escape of the contents contained therein.

In one embodiment, the mixing or contact of the various componentscauses an additional reaction, giving the user some indication that thecomponents have been contacted and that the glue has become activated.The additional reaction is something that can be observed by the user,and need not have any effect on any other property. Such reactions canbe smell, color, temperature, turbidity or cloudiness, or any otherobservable change.

The various components may be provided on the boards in a number ofmanners/locations. For example, as follows.

-   -   a. The components can be separated on the panels, such as        components (A)-(C) on one panel and (D) on the second panel. In        one embodiment, only the catalyst is provided on the second        panel.    -   b. One or more components can be encapsulated, and at least one        is not encapsulated. In this embodiment, the components are        maintained apart by their relative encapsulation, rather than by        being provided on different panels. Again, more than one        component can be provided in a single microcapsule. In one        embodiment, components (A), (B) and/or (C) are encapsulated,        and (D) is simply applied to the panel. Typically, initiator (B)        and activator (C) are not placed in the same capsule. Because        the components are inherently separated, the microcapsules and        other components all can be provided on one or both boards.    -   c. One or more of the components can be integral with the board.        In other words, one component, such as the catalyst, may be        impregnated into the structure of the panel, either only at the        edge, or mixed throughout the panel.    -   d. Multiple microcapsules can be used, wherein the components        are maintained separated by being provided in separate        microcapsules. Typically, the catalyst is provided in its own        microcapsule.    -   e. A solvent for a microcapsule can be provided in a glass        microcapsule. In this embodiment, a solvent for a microcapsule        is provided in a glass (or other inert substance which        interferes with neither any component nor the final adhesive        system) capsule. When the glass capsule is ruptured, typically        by physical pressure, the solvent is released, and such solvent        is free to act on the microcapsule(s) containing the        component(s).    -   f. The microcapsule(s) can be ruptured by heat or other external        forces. In one embodiment, either immediately before the panels        are assembled or sometime after assembly, radiation (such as        ultrasonic, heat, microwave, electromagnetic, etc.) is applied        to rupture the microcapsule(s).

The present invention teaches an improved adhesive compositionespecially suited for forming high strength dry-to-the-touch structuraladhesives. The adhesive composition of the invention, in someembodiments, is a thin layer flowable adhesive providing adry-to-the-touch adhesive providing high strength when joininginterference fit components. At least one of the adhesive constituentsflows into contact with the other constituents of the adhesivecomposition to form a high strength structural adhesive.

In a preferred embodiment a flowable monomer is encapsulated togetherwith initiator, as described by U.S. Provisional Application No.60/______, titled Encapsulated Structural Adhesive, filed Jul. 22, 2005(Atty. Docket No. 6595) in the name of Sandra Jacqueline Guinebretiereet al., herein incorporated by reference in its entirety. A flowableactivator can be separately encapsulated or positioned in a bindermaterial, matrix or carrier for the adhesive composition. Forconvenience herein, all such materials are referred to as binder orbinders herein. Upon capsule rupture, the flowable components ofmonomer, initiator and activator flow into reactive contact with eachother and a catalyst forming a high strength adhesive.

The present invention in various embodiments teaches an encapsulatedcurable adhesive composition comprising a two part curative, e.g.,activator and curative. The curative consists substantially of afirst-part curative of a preferably peroxy initiator, and a second-partcurative. Other additives can also be present such as rheologymodifiers, pigments, fragrances, odor-masking agents, fillers, colorantsand plasticizers. In one embodiment, a first population of polymericmicrocapsules encases the initiator and monomer which is reactive withthe second-part curative. The second-part curative is also of two partsor two components. The capsules encase both the first-part curative andthe monomer thereby forming a monomer and initiator (first-partcurative) blend. The polymeric microcapsules are substantiallyimpermeable to both parts of the curative. The monomer is selected fromflowable (meth)acrylate esters, epoxy(meth)acrylate andurethane(meth)acrylate esters. For convenience the term “(meth)acrylate”is to be understood as used herein and in the claims as referring toboth the acrylate and methacrylate versions of the specified monomer.However, the encapsulated monomer and initiator blend is a free flowingliquid having a viscosity of less than 500 milliPascal-second (Cp)(Centipoise). The term “monomer” in the specification and claims shouldbe understood as being defined for purposes hereof to include monomersand oligomers thereof and blends of monomers and oligomers provided therequisite viscosity parameters of the resultant blend are met. Themonomer preferably has a Tg of 35° C. or less or is blended withmonomers to have a resultant Tg of less than 35° C. The second-partcurative comprises a catalyst and activator. The second-part curative ispreferably external to the polymeric microcapsules containing monomerand initiator disposed on the substrate to be joined, or in a binder orcarrier for the system, or on the outside of the microcapsules.Alternatively, the activator of the second-part curative is separatelyencapsulated or positioned in a binder material, matrix or carrier forthe adhesive composition. The catalyst is typically external to themicrocapsules, and can be in the binder or carrier or applied as a firstcoating to a substrate which is over coated with the balance of thecomponents of the structural adhesive. Optionally, the catalyst may beseparately encapsulated or positioned in a binder material, matrix orcarrier for the adhesive composition.

An encapsulated curable adhesive composition is taught for forming highstrength structural adhesives. In the majority of embodiments, thesestructural adhesives are able to be fashioned as dry-to-the-touchcoatings before activation.

The encapsulated curable adhesive composition comprises a two partcurative comprised of a first-part curative and a second-part curative.The first-part curative is an initiator material. The second-partcurative is a catalyst and an activator. The adhesive compositionincludes a first population of polymeric microcapsules encapsulating amonomer reactive with the two part curative when “complete,” meaningthat the initiator, catalyst and activator have all come together,enabling reactive contact. The internal contents or core of the firstpopulation of microcapsules includes a flowable monomer or monomersreactive with the two part curative. Prior to encapsulation, the monomeris blended with the first-part curative forming a blend of the monomerand initiator. This blend of monomer and first-part curative forms thecore of the first population of microcapsules. The second-part curativecomprises catalyst preferably a water soluble catalyst such as a coppermetal salt, and an activator. A binder material is also provided toretain the population of microcapsules and two-part curative inproximity such as when coated on a substrate to be joined. Preferablythe activator is separately encapsulated forming a second population ofmicrocapsules.

The monomer is preferably selected from difunctional acrylates,methacrylate esters, epoxyacrylate esters, epoxyacrylates, urethaneacrylate esters, and melamine acrylate monomers and oligomers. Morepreferably the monomer is a difunctional methacrylate ester ordifunctional urethane acrylate ester. Blends of any of the foregoing arepossible.

Blends of difunctional methacrylate esters together with monofunctionalacrylate esters are also particularly useful.

The monomer and the initiator blend is selected to be a free flowingliquid, meaning a viscosity of less than 500 centipoise. The monomer andinitiator blend has a viscosity of less than 500 centipoise (Cp), (atroom temperature 25° C. unless otherwise indicated). Centipoise isequivalent to milliPascal-second units (milliPascal-second). Viscosityparameters herein are understood as measured at 25° C. unless otherwiseindicated. Similarly, the activator is preferably separatelyencapsulated and also selected to be a free flowing liquid.

Preferably the viscosity of the monomer is less than 100, and even morepreferably less than about 7 Cp (milliPascal-second); and the viscosityof the monomer and initiator blend is preferably less than 25 Cp, andmore preferably less than 10 Cp.

Most preferably the viscosity of the monomer and initiator blend is lessthan 5 Cp (milliPascal-second). A convenient way to measure viscosity isby use of a viscometer such as Brookfield, Model LVF.

The aspect of achieving a free flowing liquid of the monomer (ormonomers) and initiator which forms the internal phase or core of thefirst population of microcapsules can be accomplished by blendingmonomers of high viscosity with from 0 to 99 weight percent a lowerviscosity monomer. For illustration, melamine acrylate having aviscosity of 1500 Cp can be blended or in essence, diluted, withtetrahydrofurfuryl(meth)acrylate and hexanediol dimethacrylate(viscosity<15 Cp) in sufficient weight percent or ratio to achieve ablend with the initiator that is well below 500 Cp (milliPascal-second)making the blend useful as a free flowing liquid in the invention. Theuseful ratios of such blends to achieve the desirable viscosity of lessthan 500 Cp can be readily ascertained by the skilled artisan byblending different proportions of viscous and non-viscous monomers.

Similarly the activator is selected to be a free flowing liquid, andpreferably has a viscosity of less than 500 Cp at room temperature, andmore preferably less than 100 Cp, and most preferably less than 10 Cp.

The monomer or blend of monomers is selected to have a Tg of 35° C. orless, more preferably less than 25° C., and most preferably less than10° C. In certain applications a Tg of 1° C. or less is preferable.Similar to the technique for blending high viscosity monomers with lowerviscosity monomers, blending of high Tg monomers with lower Tg monomerscan also be done to achieve a resultant Tg for the monomer blend of 35°C. or less. Table 1 lists a variety of monomers along with their Tgvalues and viscosity. Table 1 lists a variety of monomers available fromcommercial suppliers such as Sartomer (Exton, Pa.) and others. Variousmonomers and oligomers are available commercially that either have therequisite viscosity and Tg values, or which can be blended together toachieve the requisite viscosity and Tg.

TABLE 1 Monomer Tg C. Mw viscosity Cps 25° C. or milliPascal- second2-phenoxyethyl acrylate 5 192 12 tridecyl acrylate −55 255 7difunctional aliphatic urethane acrylate 3000@60 C. urethane diacrylateoligomer −37 9975@60 C. urethane diacrylate oligomer  660@60 C. 1.6hexanediol diacrylate 43 226 9 ethoxylated (4) bisphenol diacrylate 60512 1080 caprolactone acrylate −53 344 80 urethane dimethacrylate 251740@60 C. trimethylolpropane trimethacrylate 27 338 44tetrahydrofurfuryl methacrylate 23 170 5 tetrahydrofurfuryl acrylate −15156 6 tripropylene glycol diacrylate 62 300 15 1,6 hexanedioldimethacrylate 30 254 8 polyethyleneglycol dimethacrylate 330 15 1,3butylene glycol dimethacrylate 29 226 8 ethoxylated (2) bisphenol Adimethacrylate 452 1082 ethoxylated (10) bisphenol A dimethacrylate −1808 410 caprolactone modified neopentylglycol hydroxypivalate 540 70-140 diacrylate caprolactone modified neopentylglycol hydroxypivalate768 200-300 diacrylate melamine acrylate 1500 aromatique polyetherurethane diacrylate oligomer −40 3195@60 C. TMPTA trimethylolpropanetriacrylate 62 296 106 isodecyl acrylate −60 212 5 caprolactone acrylate−53 344 80 ethoxylated bisphenol A diacrylate 60 512 1080pentaerythritol tetraacrylate 103 298 520 ethoxylated trimethylolpropanetriacrylate 103 428 60 polypropylene glycol monomethacrylate 405 35propoxylated trimethylolpropane triacrylate −15 470 90 polybutadienedimethacrylate 80%/HexaneDiol DiAcrylate ester −75  890@60 C. 20% lowviscosity polyester acrylate oligomer 1 630 polyester acrylate oligomer21 7700 epoxy acrylate oligomer 62  250@60 C. polyester acrylateoligomer −19 28 polyester acrylate oligomer 42 65 polyester acrylateoligomer −45 150 polyester acrylate oligomer −22 180 bisphenol A baseepoxy acrylate 60 2150@65 C. viscosity cps 25 C. epoxy acrylate blendedwith SR351 800 aromatic urethane acrylate 50  700@60 C. aliphaticurethane acrylate 27 660@60 C., 10080@25 C. urethane acrylate −474155@60 low viscosity diacrylate oilgomer 26 1000 aliphatic polyesterbase urethane diacrylate −38 58250@60 C.  polybutadiene dimethacrylate−39 4125@60 C. aliphatic urethane acrylate 30 60000@60 C.  methacrylatedpolybutadiene 6000 65000@45 C.  methacrylated polybutadiene, UV curableresin, soluble in water 3200 25000 epoxidized soy bean oil acrylate −2225100 trifunctional urethane acrylate 43 156000, 2800@60 C. aromaticurethane acrylate 30 15000@60 C.  aromatic polyester based urethanediacrylate 8900 polyester acrylate oligomer −20 52000 polyester acrylateoligomer, water soluble for UV wood coating 11000E@60 C.    polyesteracrylate oligomer 35 85000 aromatic urethane acrylate 35 58000 aliphaticurethane acrylate 22 6190@60 C. polybutadiene dimethacrylate 80%/HDODA20% −75  890@60 C. polyester acrylate oligomer 21 7700 epoxy acrylateoligomer 62  250@60 C. polyester acrylate oligomer 42 65 aromaticurethane acrylate 50  700@60 C. urethane acrylate −47 4155@60caprolactone modified neopentylglycol hydroxypivalate 768 200-300diacrylate urethane dimethacrylate 25 1740@60 C. melamine acrylate 1500bisphenol A base epoxy acrylate 60 2150@65 C. urethane dimethacrylate 251740@60 C. caprolactone modified neopentylglycol hydroxypivalate 768200-300 diacrylate polybutadiene dimethacrylate 80%/HexaneDiolDiAcrylate ester −75  890@60 C. 20% polyester acrylate oligomer 21 7700epoxy acrylate oligomer 62  250@60 C. polyester acrylate oligomer 42 65bisphenol A base epoxy acrylate 60 2150@65 C. aromatic urethane acrylate50  700@60 C. urethane acrylate −47 4155@60 

Viscosity of the internal phase of the capsules is adjustable byblending monomers. In this table the internal phase contains: activatorDPC 3% by weight in the monomers or initiator CHP 5% by weight in themonomers), M corresponds to THFA/HDDMA 50/50.

TABLE 2 Viscosity (cps, 25° C.) Brookfield model LVF, Monomers in theinternal phase spindle 2, 60 rpm Melamine acrylate oligomer (Doresco 15UV75° C., 1500 cps)/M 50/50 Bisphenol A base epoxy acrylate (CN120, 252150 cps @ 65° C.)/M 40/60 Urethane dimethacrylate (CN1963, 1740 cps 53@ 65° C.)/M 50/50 Polybutadiene (Ricon 130, 750 cps)/M 25 50/50

The viscocity of the internal phase is preferably lower than 100 cps.CN120 and CN1963 are products of Sartomer (Exton, Pa.). Doresco™ is atrademark of Lubrizol, Wickliffe, Ohio. DPC is diphenyl carbazone. CHPis cumene hydroperoxide. M corresponds to tetrahydrofurural methacrylate(THFA) blended with hexane diol dimethacrylate (HDDMA) in a 50/50percent ratio by weight.

TABLE 3 Activator + diluent monofunctional + difunctional monomerResultant Viscosity Resultant Tg Hexanedioldimethacrylate + <500 Cp <35°C. tetrahydrofurfural methacrylate and 3,5-1,2-dihydro-1-phenyl-2-pyropylpyridine

Table 3 is another example of blending of monomers to achieve aresultant viscosity of less than 500 Cp and resultant Tg of less than35° C.

The monomer and initiator blend is a free flowing liquid which isencapsulated and comes into reactive contact with both parts of the twopart curative when the capsules are fractured.

Reactive contact of the monomer and first-part curative with thesecond-part curative is effected by fracturing, shearing, crushing, orotherwise breaking or degrading the microcapsules so that the freeflowing monomer and first-part curative comes into contact with thesecond-part curative. Mixing occurs through flow of the free flowingmonomer and initiator from the capsule interior and flow of activatorfrom the capsule interior upon application of pressure or relativemovement of the substrates such as when an interference fit is affected.Common interference fit assemblies include threads on bolts, mortise andtenon, and various snap-fit assemblies or tongue and groove assembliesand couplers.

The monomers useful in the invention are difunctional acrylate esters,difunctional methacrylate esters and difunctional polyurethane acrylateesters and epoxy acrylates stable in the presence of initiator. Monomersshall be understood as including oligomers thereof. Optionally, aninhibitor such as hydroquinone can be added to the monomer and initiatorblend in the capsules to prevent premature polymerization.

The initiator (first-part of the two-part curative) is blended with themonomer and preferably forms the internal or core contents of the firstpopulation of polymeric microcapsules. Optionally the initiator can beseparately encapsulated though the preferred embodiment herein is ablending of the monomer and initiator and encapsulation of the blend.

Useful monomers in the invention are di- and poly-functional acrylateesters, difunctional (meth)acrylate esters, polyfunctional(meth)acrylate esters, difunctional urethane acrylate esters,polyfunctional urethane acrylate esters and polyfunctional anddifunctional epoxy acrylate monomers and oligomers used alone or incombination as blends. In alternate embodiments, optionally, the di- andpolyfunctional acrylates, methacrylates, urethane acrylates, and epoxyacrylates are further blended with monofunctional acrylates,methacrylates, urethane acrylates and epoxy acrylates.

In one form of the embodiments, the encapsulated curable adhesivecomposition is assembled as a two part system. The curative is of twoparts. The first-part curative is a free radical initiator, preferably aperoxy initiator. The initiator is preferably encapsulated together withthe monomer. Alternatively the initiator may be separately encapsulated.

A typical and preferred example of the initiator is cumenehydroperoxide. More particularly, the free radical initiator needs to besoluble or dispersible in the monomers and oligomers. The free radicalinitiator can be selected from the group of initiators comprising an azoinitiator, peroxide, dialkyl peroxide, alkyl peroxide, peroxyester,peroxycarbonate, peroxyketone and peroxydicarbonate. The free radicalinitiator can be selected from 2,2′-azobis(isobutylnitrile),2,2′-azobis(2,4-dimethylpentanenitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), 2,2′-azobis(2-methylpropanenitrile),2,2′-azobis(methylbutyronitrile), 1,1′-azobis(cyclohexanecarbonitrile),1,1′-azobis(cyanocyclohexane), benzoyl peroxide, decanoyl peroxide;lauroyl peroxide; benzoyl peroxide, di(n-propyl)peroxydicarbonate,di(sec-butyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate,1,1-dimethyl-3-hydroxybutyl peroxyneodecanoate, α-cumylperoxyneoheptanoate, t-amyl peroxyneodecanoate, t-butylperoxyneodecanoate, t-amyl peroxypivalate, t-butyl peroxypivalate,2,5-dimethyl 2,5-di(2-ethylhexanoyl peroxy)hexane, t-amylperoxy-2-ethyl-hexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxyacetate, di-t-amyl peroxyacetate, t-butyl peroxide, di-t-amylperoxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane-3, cumenehydroperoxide, 1,1-di-(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,1,1-di-(t-butylperoxy)-cyclohexane, 1,1-di-(t-amylperoxy)-cyclohexane,ethyl-3,3-di-(t-butylperoxy)-butyrate, t-amyl perbenzoate, t-butylperbenzoate and ethyl 3,3-di-(t-amylperoxy)-butyrate.

The initiator is employed at an amount of 10 percent or less by weightin the core of the capsules and more preferably from about 3 to 5percent by weight, and most preferably 0.1 to 5 percent by weight (basedon weight of the internal phase or core of the capsules).

The monomers desirably crosslink in contact with both parts of the twopart adhesive. Preferably, the first-part curative is blended with themonomer and encapsulated together with the monomer forming a firstpopulation of microcapsules. In one embodiment the second-part curativeis positioned external to the microcapsules, for example, on the outsideof the capsule wall, on a substrate to be joined, in a carrier, or abinder, with all such placements of the second curative being deemedexternal to the first population polymeric capsules. The second curativecould also be separately encapsulated forming a second population ofmicrocapsules.

The monomers for example can be selected from the group of monomers andoligomers consisting of alkene glycol dimethacrylate, alkyldimethacrylate, alkyldiol dimethacrylate, alkoxy alkanol diacrylate,trialkanol triacrylate, alkoxy(alkoxy)_(n) alkyl triacrylate,alkoxy(alkoxy)_(n) alkyl dimethacrylate, aralkyl dimethacrylate,cycloalkyl dimethacrylate, alkoxy dimethacrylate, bicycloalkyldimethacrylate, cycloalkoxy dimethacrylate, alkene glycol diacrylate,alkyl diacrylate, alkyldiol diacrylate, alkoxy alkanol dimethacrylate,trialkanol trimethacrylate, alkoxy(alkoxy)_(n) alkyl trimethacrylate,alkoxy(alkoxy)_(n) alkyl diacrylate, aralkyl diacrylate, cycloalkyldiacrylate, alkoxy diacrylate, bicycloalkyl diacrylate, cycloalkoxydiacrylate, wherein the alkyl and alkene moieties are of 1 to 16carbons, the cycloalkyl moieties are of 4 to 8 carbons, n is an integerfrom 1 to 6. Aromatic polyether urethane(meth)acrylates, aliphaticpolyester, aliphatic urethane acrylate including alkyl, alkenyl or arylsubstituted or unsubstituted urethane acrylates and epoxy acrylates canalso be advantageously employed.

More specifically, by way of illustration and not limitation, themonomers can be selected from any of hexyl dimethacrylate; triethyleneglycol dimethacrylate; ethylene glycol dimethacrylate; tetraethyleneglycol dimethacrylate; polyethylene glycol dimethacrylate; 1,3 butyleneglycol diacrylate; 1,4-butanediol dimethacrylate; 1,4-butanedioldiacrylate; diethylene glycol diacrylate; diethylene glycoldimethacrylate; 1,6 hexanediol diacrylate; 1,6 hexanedioldimethacrylate; neopentyl glycol diacrylate; neopentyl glycoldimethacrylate, polyethylene glycol diacrylate; tetraethylene glycoldiacrylate; triethylene glycol diacrylate; 1,3 butylene glycoldimethacrylate; tripropylene glycol diacrylate; ethoxylated bisphenoldiacrylate; ethoxylated bisphenol dimethyacrylate; dipropylene glycoldiacrylate; alkoxylated hexanediol diacrylate; alkoxylated cyclohexanedimethanol diacrylate; propoxylated neopentyl glycol diacrylate,trimethylolpropane trimethacrylate; trimethylolpropane triacrylate,pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate,propoxylated trimethylolpropane triacrylate, propoxylated glyceryltriacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritolpentaacrylate, ethoxylated pentaerythritol tetraacrylate, and the like,and mixtures thereof.

Monofunctional acrylates, methacrylates and urethane acrylates, urethanemethacrylates for blending with the monomer include, by way ofillustration and not limitation, monomers and oligomers of alkylacrylate, aralkyl acrylate, cycloalkyl acrylate, alkoxy acrylate,cycloalkoxy acrylate, bicycloalkyl acrylate, alkoxy(alkoxy)_(n)acrylate, alkyl methacrylate, polyalkene(meth)acrylate, aralkylmethacrylate, cycloalkyl methacrylate, alkoxy methacrylate, bicycloalkylmethacrylate, cycloalkoxy methacrylate, and alkoxy (alkoxy)methacrylate.The alkyl moieties should be selected preferably of 1 to 16 carbons, thecycloalkyl moieties from 4 to 8 carbons, and n is an integer from 1 to6.

More particularly the monofunctional acrylates, methacrylate or urethaneacrylates or methacrylates can be selected from n-pentyl acrylate,2-methyl butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate,n-decyl acrylate, n-dodecyl acrylate, lauryl methacrylate, laurylacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, iso-octylacrylate, iso-octyl methacrylate, isononyl acrylate, isodecyl acrylate,2-ethoxyethyl methacrylate; butyl diglycol methacrylate;tetrahydrofurfuryl acrylate; tetrahydrofurfurylmethacrylate; furfurylmethacrylate 2-phenoxyethyl acrylate, isohexyl acrylate; tridecylacrylate; tridecyl methacrylate; ethoxylated nonyl phenol acrylate andthe like and mixtures thereof.

The catalyst is an organic acid or a salt of a transition metal or ametal ion. The catalyst optionally can be separately encapsulated.Preferred are copper salts such as copper chloride. Organo copper saltscan also be advantageously employed such as copper acetyl acetonate andcopper ethyl hexanoate. Optionally the catalyst such as copper salts canbe encapsulated with the activator, or optionally even separatelyencapsulated.

The catalyst is used at about less than 2 percent and more preferably0.2 to 1 wt. percent (based on weight of the reactive constituentsmaking up the adhesive).

An activator, preferably separately encapsulated is included. Usefulactivators to be used in combination with the catalyst and firstpopulation of microcapsules include ferrocene, butyl ferrocene,diethylferrocene, amino rhodanine, diphenyl carbazone, diphenylcarbazide, dithizone, guaiazulene.

More particularly, the activator is an organonitrogen compound such astertiary amine, amide and imide compounds, aliphatic amines, aldehydeamines, aromatic amines. Specific examples include, without limitation,acetylphenyl hydrazine, diphenyl carbazide, diphenyl carbazone,dithizone, propyl dihydropyrridine, acetaldehyde-benzylamine,butyraldehyde aniline, benzylamine, various dialkyl amines such asdialkylamine, aniline, toluidine, hexamethylene tetramine,polyethyleneimine, aminorhodanine, tetramethylthiourea,mercaptobenzothiazole, and the like.

The activators are used at preferably less than 10 percent by weight,and more preferably from 1 to 5 percent by weight of the reactiveadhesive composition (excluding weight of binder and wall material).

Microcapsules are obtained by providing an aqueous mixture containing acolloidal dispersion of hydrophilic wall-forming material and monomerswith initiator.

High shear agitation is applied to the aqueous mixture to achieve aparticle size of the core material of about 0.1 to 250μ (250 microns),preferably 0.1 to 100 microns and more preferably 0.1 to 50 microns.Smaller capsules of 10μ or less can be produced for specializedapplications.

Common microencapsulation processes can be viewed as a series of steps.First, the core material which is to be encapsulated is emulsified ordispersed in a suitable dispersion medium. This medium is preferablyaqueous but involves the formation of a polymer rich phase. Mostfrequently, this medium is a solution of the intended capsule wallmaterial. The solvent characteristics of the medium are changed such asto cause phase separation of the wall material. The wall material isthereby contained in a liquid phase which is also dispersed in the samemedium as the intended capsule core material. The liquid wall materialphase deposits itself as a continuous coating about the disperseddroplets of the internal phase or capsule core material. The wallmaterial is then solidified. This process is commonly known ascoacervation.

Gelatin or gelatin-containing microcapsule wall material is well known.The teachings of the phase separation processes, or coacervationprocesses which are described in U.S. Pat. Nos. 2,800,457 and 2,800,458are incorporated herein by reference. Uses of such capsules aredescribed in U.S. Pat. No. 2,730,456.

In-situ polymerization, microcapsule walls are formed from materialspresent in a discontinuous phase. Thus, the wall forming materialsdispersed into the discontinuous phase polymerize and migrate outward tothe interface between the discontinuous and continuous phases, resultingin the formation of microcapsule wall. Known techniques of in-situpolymerization include free radical polymerization and the incorporationof reactive polyisocyanates and polyol compounds within thediscontinuous phase.

More recent processes of microencapsulation involve, and preferredherein, are the polymerization of urea and formaldehyde, monomeric orlow molecular weight polymers of dimethylol urea or methylateddimethylol urea, melamine and formaldehyde, monomeric or low molecularweight polymers of methylol melamine or methylated methylol melamine, astaught in U.S. Pat. No. 4,552,811 incorporated herein by reference.These materials are dispersed in an aqueous vehicle and the reaction isconducted in the presence of acrylic acid-alkyl acrylate copolymers. Themicrocapsule can be formed from materials comprising gellable colloids,carboxymethyl cellulose, gelatin, gelatin-gum arabic, methylatedmethylol melamine resin, melamine formaldehyde, dimethylol urea, ureaformaldehyde, methylol melamine, methylated dimethyl urea, a gelatinanionic polymer, alkyl acrylate-acrylic acid copolymer or othercommonly-used polymeric materials used in coacervation.

The invention is not limited to one manner of microencapsulation.Processes of microencapsulation are now well known in the art. U.S. Pat.Nos. 2,730,456, 2,800,457; and 2,800,458 describe methods for capsuleformation. Other useful methods for microcapsule manufacture are: U.S.Pat. Nos. 4,001,140; 4,081,376 and 4,089,802 describing a reactionbetween urea and formaldehyde; U.S. Pat. No. 4,100,103 describingreaction between melamine and formaldehyde; British Pat. No. 2,062,570describing a process for producing microcapsules having walls producedby polymerization of melamine and formaldehyde in the presence of astyrenesulfonic acid. Microcapsules are also taught in U.S. Pat. Nos.2,730,457 and 4,197,346. The more preferred process for formingmicrocapsules are from urea-formaldehyde resin and/or melamineformaldehyde resin as disclosed in U.S. Pat. Nos. 4,001,140; 4,081,376,4,089,802; 4,100,103; 4,105,823; 4,444,699 or most preferably alkylacrylate-acrylic acid copolymer capsules as taught in U.S. Pat. No.4,552,811. Each patent described is incorporated herein by reference tothe extent each provides guidance regarding microencapsulation processesand materials.

Preferably the capsules employed are from 0.1 to 100 microns, preferably1 to 50 microns, more preferably less than 40, and most preferably lessthan 30 microns. Other sizes are possible for specific applications.

The first step in the encapsulation process is the preparation of thediscrete droplets or domains of the monomer in the dispersion medium.Preferably the initiator is blended first with the monomer. Where suchmaterials are in solution or liquid form and the encapsulation is to beby way of, e.g., coacervation, interfacial polymerization, etc., thedispersion medium solution or liquid containing the monomer andinitiator is subjected to high shear mixing or agitation to create asuspension, emulsion or colloidal system of discrete domains of themonomers and initiator blend of the requisite size. The catalyst of thesecond-part curative can be incorporated into a solid binder orsubstantially solid carrier, and the carrier or binder may be ground andsorted to a desired particle size. A film forming binder or carrier ispreferred through solvent solubilized solids can also be employed. Theactivator of the second-part curative is preferably in separatemicrocapsules.

A useful microencapsulation technique is coacervation wherein thematerial to be encapsulated (monomer and first-part curative) isdispersed or emulsified in a liquid solution of the material to be usedas the wall material. The solution is perturbed to cause a phaseseparation of the wall material, or at least a portion thereof, from thesolvent with all or some of the wall material coating the dispersedmaterial to be encapsulated. In this process, the wall forming materialmay directly separate out onto the emulsified or dispersed core materialor it may form its own emulsion with the droplets of the wall materialsubsequently depositing on the droplets of the core material. In eithercase, the liquid wall material deposits itself as a continuous coatingabout the dispersed droplets of the internal phase or capsule corematerial of monomers and initiator and the wall material is thensolidified. Solution perturbation can be any that affects the solubilityof the wall material including changes in temperature and addition ofanother solvent, including, for example, the addition of a non-solventfor the wall material. It should be readily understood by those skilledin the art that the foregoing may be accompanied by a pH shift with wallmaterials such as gelatin to promote the phase separation in the wallformation step, as taught in Green (U.S. Pat. Nos. 2,800,457 and2,800,458, incorporated herein by reference).

In coacervation encapsulation, the material to be coated is typically aliquid and is emulsified in the solvent to form droplets which are thencoated with the wall material. Oftentimes it is advantageous to alsoemploy an emulsification agent to assist with the emulsification of thecarrier materials or precursors thereof. Preferred emulsification agentsthat can be used are amphiphilic, that is, they contain both hydrophilicand hydrophobic groups in the same molecule. Exemplary emulsificationagents include, but are not limited to, partially hydrolyzed polyvinylalcohol, starch derivatives, cellulose derivatives, polyacrylamide, andthe like. A preferred emulsification agent for use in the invention ispartially hydrolyzed polyvinyl alcohol or polyacrylic acid. Polyacrylicacid used as a stabilizer with polyamide wall material was particularlypreferable. In a preferred method, high shear agitation is provided tothe aqueous mixture to achieve a droplet size of less than about 250microns, preferably less than 100 microns.

The conditions for encapsulation will vary based upon the choice of thematerial used for the capsule wall. Suitable materials for the capsulewalls include natural materials such as gelatin, gum arabic, starches,shellac, and rosin, polymers such as polyvinyl alcohol, polyethylene,polypropylene, polystyrene, polyacrylamides, polyethers, polyesters,polyamides, polybutadiene, polyisoprene, silicones, epoxies,polyurethanes, formaldehyde resins such as reaction products offormaldehyde with phenols, urea, and melamine, and copolymers such aspolyurethane copolyethers. Alkylacrylate-acrylic acid copolymer is apreferred wall material.

Dyes, pigments, fillers, plasticizers, binding agents, and otheradditives can be incorporated in the microcapsule wall or applied to themicrocapsule wall surface. One important parameter to keep in mind whenformulating wall materials is permeability. Generally, the wall materialshould have low permeability, at least with respect to the material tobe encapsulated. No or low permeability of the capsule wall isparticularly important with respect to the second-part curative in thebinder or external to the capsules so as to prevent loss of the curativeand premature polymerization of the curable composition. Likewise, itmay be important for the microcapsule wall to be impermeable or of lowpermeability to the curable component of the curable composition so asto prevent any ingress of the same of external materials. Dependent uponthe encapsulated material, it may also be desirable to formulate thewall material to have low permeability to certain gases such as oxygenor low permeability to liquids such as water or solvents such as tolueneor tetrahydrofuran. The requisite permeation rates will vary for eachsystem, but can be met by judicious choice of the wall material and bydegree of crosslinking of the wall material. Generally, as crosslinkingincreases, the permeation rate decreases.

The microcapsule walls can comprise less than 15 percent and preferablyfrom 5 to 10 percent by weight of the encapsulated components.

Optionally the microcapsules with monomer and first-part curative, andthe second-part curative metal catalyst are dispersed in a binder oradhered to a surface by the binder. The second-part curative activatoris separately microencapsulated and also dispersed in the binder oradhered to a surface by the binder. It is to be understood in thiscontext that there are two populations of microcapsules. The firstpopulation of microcapsule includes the first-part curative (initiator)with monomer as the capsule core contents. The second-part curativecomprises catalyst external to the microcapsules and a second populationof microcapsules with activator, preferably a hydrophobic activator. Thebinder could constitute a carrier material for the capsules. Preferablythe binder is a polymeric material or selected from almost any adherentmaterial and preferably selected from binder materials such aspolyvinylalcohol, starches, modified starches, gelatin, hydroxylethylcellulose, methyl cellulose, methyl-hydroxypropyl cellulose, orselected from many film forming materials such as carboxylated polyvinylalcohols, polyacrylates, urethanes, polyvinylacetates, vinyl acetateethylene copolymers, carboxylated vinyl acetate, polystyrene, or variousfilm forming latexes. The binder is preferably used in an amountsufficient to hold the adhesive constituents or capsules onto thesubstrate but less than an amount that would interfere with adhesion ofthe formed adhesive when the capsules are ruptured and the contents comeinto reactive contact.

Various additives such as rheology modifiers, rheology aids, tackifiers,plasticizers, rubberized particles, styrene-butadiene rubber lattices,lubricants, toners, coloring agents, can be optionally employed.

Optionally, as an alternative embodiment the binder material can beselected to be UV curable binders include materials such as thosecurable using electron beam, UV radiation or visible light, such asacrylated monomers or oligomers of acrylated epoxy resins, acrylatedurethanes and polyester acrylates and acrylated monomers includingmonoacrylated, multiacrylated monomers, and thermally curable resinssuch as phenolic resins, urea/formaldehyde resins and epoxy resins, aswell as mixtures of such resins. The curing mechanism through UV lightcan be employed with or without the assistance of an additional thermalcure mechanism. In the context of this application it is understood thatthe term “radiation curable” embraces the use of visible light, orultraviolet (UV) light, and electron functions and radiation curefunctions can be provided by different functionalities in the samemolecule.

If UV cure of the binder is desired, generally any UV-curable binder maybe chosen. Examples of suitable binders also include unsaturatedpolyester resin and alkyl resins, unsaturated melamine formaldehyderesins, polybutadiene resins, and unsaturated compounds such as(meth)acrylates and allyl compounds.

Examples of UV-curable polyesters include polycondensation products fromunsaturated di- or polycarboxylic acids or derivatives thereof, forinstance: maleic acid, maleic anhydride and/or fumaric acid, and polyolssuch as ethylene glycol, 1,2-propane diol, diethylene glycol, hexanediol, glycerol, trimethylol propane or pentaerythritol. These polyesterscan be blended with ethylenically unsaturated monomeric compounds, suchas methacrylic compounds and vinyl compounds, including acrylatecompounds and allyl compounds.

Illustrative UV curable (meth)acrylates and allyl compounds includemethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate; (meth)acrylic esters of aliphatic diolsand/or polyols, for instance: ethylene diacrylate, trimethylol propanetriacrylate and pentaerythritol tetraacrylate; hydroxyl(meth)acrylatessuch as hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropylmethacrylate, 4-hydroxybutyl acrylate and pentaerythritol triacrylateand allyl compounds such as diallyl phthalate, diallyl maleate, triallylisocyanurate and ethylene glycol diallyl ether.

A desirable UV binder is urethane acrylate resin, more particularly atleast one isocyanate group-containing adduct of (a) an acrylic ormethacrylic hydroxyl ester having 5 to 20 carbons atoms and (b) apolyisocyanate having 4 to 44 carbon atoms and 2 to 4 isocyanate groups.As examples of suitable isocyanate compounds may be mentionedhexamethylene diisocyanate, 2,2,4-trimethylhexane-1,6-diisocyanate,2,4,4-trimethylhexane-1,6-diisocyanate, and cyclohexyl-1,4-diisocyanate,or the adduct of hexamethylene diisocyanate.

Suitable photoinitiators include for example: aromatic carbonylcompounds such as benzyl, benzyl dimethyl ketal, acetophenone,substituted acetophenones, thioxanthone chlorothioxanthone andpreferably benzophenone. Optionally, use may be made of compounds suchas aromatic azo compounds and compounds such as benzoin and ethersthereof, such as the methyl ether, the ethyl ether, the propyl ether andthe t-butyl ether. Mixtures of photoinitiators may also be used.

The photoinitiator is usually present in an amount of 0.05 to 10% byweight, based on the UV-curable binder. Some free radicalpolymerizations are inhibited by oxygen and may require provision of aninert atmosphere. Microencapsulation of components can help to restrictoxygen contact.

Preferably the binder in a UV reactive system is a reactive oligomer orprepolymer which polymerizes when subjected to UV radiation in thepresence of a suitable initiator. An optional component of the bindercan be commonly employed diluents which modify the cure rate and, forexample, the viscosity of the uncured composition. The binder must becapable of adhering to the substrate on curing, but it should of coursealso wet or adhere to the substrate before curing.

The following is an illustrative example of a UV curable binder. CNmonomers are products of Sartomer (Exton, Pa.): CN550 (amine modifiedpolyether acrylate oligomer) 53.2% by weight; CN501 (amine modifiedpolyether acrylate oligomer) 22.8%; CN976 (aromatic urethane diacrylate)20%; CN385 (benzophenone) 2%; and Irgacure 184 (photoinitiator) 2% (CibaSpecialty Chemicals). Viscosity at 25° C. is about 2000 mPa.

The components of the second-part curative preferably are water solubleor water dispersible and are preferably external to the capsules. Thecomponents that are hydrophobic or oil soluble are preferably internalto the capsules. Most preferably the activator is selected to behydrophobic and is separately encapsulated in a second population ofmicrocapsules, separate and distinct from the first population ofmicrocapsules encapsulating the monomer and first curative comprisinginitiator.

The second-part curative comprises a catalyst and activator. Thesecond-part curative is external to the first population of polymericmicrocapsules, on the outside capsule wall, or in the binder. In oneembodiment, the monomer is a difunctional methacrylate, and the monomercan include in addition a monofunctional methacrylate, such as furfurylmethacrylate. The difunctional methacrylate is preferably butyleneglycol dimethacrylate, or hexane diol dimethacrylate.

Looking now at the drawings, FIG. 1 depicts an embodiment according tothe invention. Monomer, and initiator which is the first-part curative,form the core of microcapsules 1, referred to herein as the firstpopulation of microcapsules. Catalyst 2A, a metallic salt or organicacid or metal ion, is shown outside of microcapsules 1. Sizes areexaggerated.

Activator 2B such as a tertiary amine, imide or amide can be separatelyencapsulated to form a second population of microcapsules. Themicrocapsule 5 for activator 2B in FIG. 1 is depicted using dotted linessince the encapsulation is optional. Other optional configurations foractivator 2B include the arrangement of FIG. 4 wherein activator 2B isshown dispersed in a binder material 4′ or carrier. The binder materials4, 4′, and 4″ can be the same or different binders. The binder canconstitute a matrix material or foam that temporarily isolates activator2B from catalyst 2A.

An alternative arrangement with larger partial separation of catalyst 2Afrom activator 2B is depicted in FIG. 5. The binder materials 4, 4′ and4″ can each be the same or different binders.

FIG. 2 illustrates the curable composition of the invention as a coatingonto substrate 3 which can be any relatively rigid material such asglass, hardwood, fiberboard, plywood, oriented strandboard (OSB),chipboard, fiberglass, polymeric, natural or synthetic, composites suchas fibers dispersed in various matrices such as resins, metals, orceramics. The substrate should be selected to be receptive to theadhesive composition and should be tested for forming strong bondingwith the adhesive composition. Medium-density fiberboard (MDF) andhigh-density fiberboard are suitable examples of fiberboard.

In FIG. 2 catalyst 2A and activator 2B are shown dispersed in bindermaterials 4 and 4′ respectively. Microcapsules 1 with monomer andinitiator core are shown adhered to binder material 4′.

Dimensions are exaggerated in the drawings. The quantity of the binderis exaggerated and can be optionally limited to that quantity necessaryto adhere the components of the adhesive system. It is therefore notalways necessary to envelope the catalyst or activator, especially ifthese constituents are separately encapsulated.

FIG. 3 is an alternative embodiment wherein microcapsules 1 containingmonomer and the first-part curative are dispersed in binder material 4′overcoated over lower binder material layer 4. The binder materials canbe the same or different. Microcapsules 1 containing monomer and thefirst-part curative form a first population of microcapsules. A secondpopulation of microcapsule 5 is (shown smaller in size and ellipsoid inshape for purposes of illustration. Size selection is optional and canbe selected to be larger than the first population of microcapsules).The second population of microcapsules contain activator 2B within thecore.

In FIG. 3, as a further alternative, the capsules 1, activator 2B,catalysts 2A can optionally be uniformly or chaotically dispersed in asingle binder material 4 forming a single layer adhesive coating. Thesingle layer adhesive coating is often preferable and most economic.

In FIG. 4 microcapsules 1 contain monomer and the first-part curative.The second-part curative of catalyst 2A and activator 2B is illustratedas dispersed in separate layers of binder material 4 and 4′. Bindermaterials 4, 4′ and 4″ can be the same or different in each layer.Microcapsules 1 are shown in the top binder layer 4″. Alternatively,microcapsules 1 can be dispersed throughout any of the binder materiallayers.

In FIG. 4 activator 2B is a lower layer and catalyst 2A forms a middlelayer or is dispersed in a binder 4.

In FIG. 5 the second-part curative is disposed on opposite sides of thebinder layer with microcapsules containing monomer and the first-partcurative. Catalyst 2A is depicted below capsules 1, and activator 2B isillustrated applied as an overcoat on the opposite side of capsules 1 inbinder 4″. Optionally binder 4″ can be omitted if adherence via binders4′ and 4 is sufficient to hold capsules 1, activator 2B and catalyst 2Ain place.

FIG. 6 illustrates alternative embodiments A and B where the componentsof the adhesive system are coated onto separate surfaces 6 and 7.Surfaces 6 and 7 can take the form of a variety of mating orinterlocking configurations such as the thread surfaces of a bolt andnut, mortise and tenon, dovetail, interlocking tongue and groove,snap-lock parts, male and female couplers, and various otherconfigurations bringing at least two surfaces into proximate contact.Surfaces 6 and 7 can include a tab and corresponding recess, detent,friction fit or other mechanical interlock to facilitate holding thesurfaces in place until the adhesive cures or sets. The adhesive systemof the invention provides a dry-to-the-touch adhesive that canfacilitate more permanent joining and assembly.

In FIG. 6 version A capsules 1 with first-part curative are shownapplied to at least one face of surface 7. Catalyst 2A is also shownapplied along with the first population of capsules 1.

A second population of capsules 5 encapsulating activator 2B are appliedto at least one face of surface 6.

In FIG. 6, an alternative embodiment is also illustrated as version Bwherein the catalyst 2A is applied to a face of surface 6 with thesecond population of capsules 5 which encapsulate activator 2B.Sufficient binder (not shown) should be utilized to adhere capsules 1and 5 and catalyst 2A to hold them in position until the capsules areruptured. This allows the free flowing liquid contents of the capsulesto come into reactive contact such that the first-part curative andsecond-part curative can react with the monomer forming the structuraladhesive.

As a yet further alternative embodiment, capsules 1 and 5 can be appliedwith binder to one or the same surface, and a catalyst 2A can be appliedto a mating surface. All such variations are within the scope of theinvention.

The examples herein are considered to illustrate the invention andshould not be considered as limiting. In the examples all parts orproportions are by weight and all measurements are in the metric system,unless otherwise indicated.

EXAMPLE 1 Preparation of Microcapsules Containing 5% Initiator inInternal Phase

The composition of the capsules is as follows:

Internal Phase (IP) Hexanedioldimethacrylate, 156.9 g Tetrahydrofurfurylmethacrylate, 17.4 g Cumene hydroperoxide (CHP) 9.2 g 1^(st) WaterPhase: Deionized water, 112 g Acrylic acid butyl acrylate copolymer,17.5 g 5% NaOH aqueous solution 14.1 g methoxymethyl methylol melamine2.9 g 2^(nd) Water Phase Deionized water 33.0 g Polyacrylic acid 6.1 gMethoxymethyl methylol melamine 17.4 g

A procedure for preparing microcapsules is as follows. The 1^(st) WaterPhase was prepared according to the composition as listed above, and pHof the aqueous solution was adjusted to 5.82 with 5% sodium hydroxidesolution, and maintaining the temperature of the solution at 65° C. Thenthe premixed internal phase was pre-heated to 65° C. was pre-emulsifiedinto the 1^(st) Water Phase by high shear agitation at 800 rpm to forman emulsion and then milled at 1700 rpm with a high shear milling bladeuntil an emulsion droplet size of 14 μm was obtained as analyzed by aModel 780 Accusizer. Thereafter, the 2^(nd) Water Phase was added to theemulsion along with 2.2 grams of sodium sulfate. The emulsion was mixedand maintained at 65° C. for 8 hrs. An average capsule size of 14.8 μmwas obtained.

EXAMPLE Preparation of Microcapsules Containing 2.5% Initiator inInternal Phase

The composition of and the procedures for preparing the microcapsulesare the same as in Example 1 except for the following:

Internal Phase (IP) Hexanedioldimethacrylate, 161.0 g Tetrahydrofurfuryl methacrylate, 17.9 g Cumene hydroperoxide (CHP) 4.58g

EXAMPLE 3 Preparation of Microcapsules Containing 1.5% Initiator inInternal Phase

The composition of and the procedures for preparing the microcapsulesare the same as in Example 1 except for the following:

Internal Phase (IP) Hexanedioldimethacrylate, 162.6 g Tetrahydrofurfuryl methacrylate, 18.1 g Cumene hydroperoxide (CHP) 2.75g

EXAMPLE 4 Preparation of Microcapsules Containing 5% Initiator inInternal Phase

The composition of and the procedures for preparing the microcapsulesare the same as in Example 1 except for the following:

1^(st) Water Phase: Deionized water, 112 g Acrylic acid butyl acrylatecopolymer, 9.1 g 5% NaOH aqueous solution 14.1 g methoxymethyl methylolmelamine 2.9 g 2^(nd) Water Phase Deionized water 33.0 g Polyacrylicacid 6.1 g Methoxymethyl methylol melamine 8.8 g

EXAMPLE 5 Preparation of Microcapsules Containing 5% Initiator inInternal Phase

The composition of and the procedures for preparing the microcapsulesare the same as in Example 1 except for the following:

Internal Phase (IP) Hexanedioldimethacrylate, 139.5 g Tetrahydrofurfurylmethacrylate,  34.8 g Cumene hydroperoxide (CHP)  9.2 g

EXAMPLE 6 Preparation of Microcapsules Containing 1% Activator inInternal Phase

The composition of the capsules is as follows:

Internal Phase (IP) Hexanedioldimethacrylate, 163.5 g Tetrahydrofurfurylmethacrylate, 18.2 g 3,5-diethyl-1,2-dihydro-1-phenyl- 1.83 g (1%)2-pyropyl pyridine, 1^(st) Water Phase: Deionized water, 112 g Acrylicacid butyl acrylate 17.8 g copolymer, 5% NaOH aqueous solution 13.6 gmethoxymethyl methylol melamine 2.9 g 2^(nd) Water Phase Deionized water32.0 g Polyacrylic acid 6.1 g Methoxymethyl methylol 17.2 g melamine

A procedure for preparing microcapsules is as follows. The 1^(st) WaterPhase was prepared according to the composition as listed above, and pHof the aqueous solution was adjusted to 5.82 with 5% sodium hydroxidesolution, and temperature of the solution was maintained at 65° C. Thenthe premixed internal phase pre-heated to 65° C. was emulsified into the1^(st) Water Phase by mixing at 700 rpm to form an emulsion, and thenmilled at 1700 rpm with a high shear milling blade. After milling for 15min, the 2^(nd) Water Phase was added to the emulsion along with 2.2grams of sodium sulfate. The emulsion was mixed and maintained at 65° C.for 8 hrs. An average capsule size of 15.4 μm was obtained as analyzedby a Model 780 Accusizer.

EXAMPLE 7 Preparation of Microcapsules Containing 5% Activator inInternal Phase

The composition of the capsules is as follows:

Internal Phase (IP) Hexanedioldimethacrylate, 108 g Tetrahydrofurfurylmethacrylate, 12 g 3,5-diethyl-1,2-dihydro-1-phenyl- 6 g (5%) 2-pyropylpyridine, 1^(st) Water Phase: Deionized water, 104 g Acrylic acid butylacrylate 18 g copolymer, 5% NaOH aqueous solution 14 g methoxymethylmethylol melamine 3.0 g 2^(nd) Water Phase Deionized water 32.0 gPolyacrylic acid 6.0 g Methoxymethyl methylol 17.7 g melamine

A procedure for preparing microcapsules is as follows. The 1^(st) WaterPhase was prepared according to the composition as listed above, and pHof the aqueous solution was adjusted to 5.82 with 5% sodium hydroxidesolution, and temperature of the solution was maintained at 65° C. Thenthe premixed internal phase pre-heated to 65° C. was emulsified into the1^(st) Water Phase by a mixer at 700 rpm to form an emulsion, and thenmilled at 1500 rpm with a high shear milling blade until an emulsiondroplet size of 14 μm was obtained as analyzed by a Model 780 Accusizer.Thereafter, the 2^(nd) Water Phase was added to the emulsion along with2.3 grams of sodium sulfate. The emulsion was mixed and maintained at65° C. for 8 hrs. An average capsule size of 15.4 μm was obtained.

EXAMPLE 8 Preparation of Microcapsules Containing Only Activator inInternal Phase

The composition of the capsules is as follows:

Internal Phase (IP) 3,5-diethyl-1,2-dihydro-1-phenyl-2-  183 g pyropylpyridine, 1^(st) Water Phase: Deionized water,  112 g Acrylic acid butylacrylate copolymer, 17.8 g 5% NaOH aqueous solution 13.6 g methoxymethylmethylol melamine  2.9 g 2^(nd) Water Phase Deionized water 32.0 gPolyacrylic acid  6.1 g Methoxymethyl methylol melamine 17.2 g

A procedure for preparing microcapsules is as follows. The 1^(st) WaterPhase was prepared according to the composition as listed above, and pHof the aqueous solution was adjusted to 5.82 with 5% sodium hydroxidesolution, and temperature of the solution was maintained at 65° C. Thenthe premixed internal phase pre-heated to 65° C. was emulsified into the1^(st) Water Phase by a mixer at 700 rpm to form an emulsion, and thenmilled at 1500 rpm with a high shear milling blade. After milling for 15mins, the 2^(nd) Water Phase was added to the emulsion along with 2.2grams of sodium sulfate. The emulsion was mixed and maintained at 65° C.for 8 hours. An average capsule size of 16.4 μm was obtained as analyzedby a Model 780 Accusizer.

EXAMPLE 9 Preparation of Microcapsules Containing 5% Activator inInternal Phase

The composition of and the procedures for preparing the microcapsulesare the same as in Example 7 except for the following:

1^(st) Water Phase: Deionized water, 112 g  Acrylic acid butyl acrylatecopolymer, 9.1 g 5% NaOH aqueous solution 14.1 g  methoxymethyl methylolmelamine 2.9 g 2^(nd) Water Phase Deionized water 33.0 g  Polyacrylicacid 6.1 g Methoxymethyl methylol melamine 8.8 g

EXAMPLE 10 Preparation of Microcapsules Containing Only Activator inInternal Phase

Internal Phase: PDHP (3,5-diethyl-1,2-dihydro-1-phenyl- 290 g 2-pyropylpyridine) Water Phase I water 230.4 g Acrylic acid butyl acrylatecopolymer 3.0 g 5% NaOH 22.1 methoxymethyl methylol melamine 4.8 g WaterPhase II water 126 g Polyacrylic acid 10.1 g Methoxymethyl methylolmelamine 29.5 g

A general procedure of capsule manufacture is described. 290 grams of3,5-diethyl-1,2-dihydro-1-phenyl-2-pyropyl pyridine (PDHP) is selectedas an internal phase.

A first water phase is prepared of 230.4 grams water 3 grams of acrylicacid butylacrylate copolymer, and 4.8 grams methoxymethyl methylolmelamine. pH is adjusted to 5.68 with 5% NaOH.

A second water phase is prepared of 126 grams of water, 10.1 gramspolyacrylic acid, and 29.5 grams methoxymethyl methylol melamine.

Water phase I is maintained at 65° C. with stirring (500 rpms). Theinternal phase is added and stirring increased to blend at high speed toachieve an emulsion size of 27.1 μm.

The second water phase is added along with 3.8 grams Na₂SO₄ and themixture heated for 8 hours at 65° C. Capsules of approximately 26 μm.size are obtained.

EXAMPLE 11 Adhesive Coating Formulation

Capsules containing initiator and capsules containing activator weremixed with catalyst and binders, and were coated on cellulosic substratemade of high density fiber boards. Alternatively catalyst may bepre-applied on the substrate, mixed in the liquid coating formulation,or applied in both. The binder used was a vinyl acetate-ethylenecopolymer latex. After the coating was dried, two pieces of substratewith the coating applied using a snap-fit tongue and groove assemblywere mated together, and the compression fit exerted sufficient shearforce to break the capsules in the coating, resulting in reactivecontact among initiator, activator, monomers and catalyst. Table 4 showsthe bonding strength tested with an EJA Materials Tester (Thwin-AlbertCompany).

TABLE 4 Bonding strength with different adhesive formulations CapsuleRatio of Copper Initiator Activator Initiator to Copper in slurryStrength Test # Capsules Capsules Activator Binder (%) pre-coat (ppm)(N) 1 Example 1 Example 7 1/1 0 Yes 740 0 2 Example 1 Example 7 1/1 0Yes 1480 0 3 Example 1 Example 7 1/1 5 Yes 740 89 4 Example 1 Example 71/1 5 Yes 1480 519 5 Example 1 Example 7 1/1 5 No 4400 510 6 Example 4Example 9 1/1 0 Yes 1480 396 7 Example 4 Example 9 1/1 5 Yes 1480 670 8Example 1 Example 6 1/2 0 No 1480 0 9 Example 1 Example 6 1/2 0 Yes 1480869 10 Example 1 Example 6 1/2 5 Yes 1480 921 11 Example 1 Example 8 1/99 5 Yes 1480 719 12 Example 1 Example 8  5/95 5 Yes 1480 284 13Example 1 Example 8 10/90 5 Yes 1480 191 14 Example 2 Example 8  1/99 5Yes 1480 633 15 Example 3 Example 8  1/99 5 Yes 1480 636 16 Example 5Example 10  1/99 5 No 4400 950

EXAMPLE 12 Initiator and Activator Capsules Coated on SeparateSubstrates

Capsules containing initiator and capsules containing activator may beseparately formulated with other coating components, such as catalystand binders. In the following table, these were coated on separatesubstrates to be bonded. Table 5 shows bonding strength tested with anEJA Materials Tester (Thwin-Albert Company).

TABLE 5 Bonding strength for capsules coated on separate substratesCapsule Ratio of Copper Strength Initiator Activator Initiator to BinderCopper in slurry (N) Test # Capsules Capsules Activator (%) pre-coat(ppm) (Newtons) 1 Example 1 Example 7 1/1 0 Yes 1480 156 2 Example 1Example 7 1/1 5 Yes 1480 442 3 Example 1 Example 6 1/2 0 Yes 1480 772 4Example 1 Example 6 1/2 5 Yes 1480 961 5 Example 1 Example 8  1/99 5 Yes1480 896 6 Example 5 Example 10  1/99 5 No 4400 966

EXAMPLE 13 Different Binders

Many different kinds of binder materials can be used in the coatingformulation. They should be able to hold capsules and other componentsof the coating in place, and has no adverse effect on bonding strength.The following binders were tested:

A—Vinyl acetate-ethylene copolymer

B—Acrylic latex

C—Carboxylated vinyl acetate resin

D—Polyvinyl acetate

TABLE 6 Bonding strength with different binders Capsule Ratio of CopperInitiator Activator Initiator to Copper in slurry Strength BindersCapsules Capsules Activator Binder (%) pre-coat (ppm) (N) A Example 1Example 7 1/1 5 Yes 1480 790 B Example 1 Example 7 1/1 5 Yes 1480 595 CExample 1 Example 7 1/1 5 Yes 1480 775 D Example 1 Example 7 1/1 5 Yes1480 560

EXAMPLE 14

Viscosity of monomer blends as the internal phase of capsules. Mcorresponds to THFA/HDDMA 50/50 ratio

Viscosity (cps. 25° C.) Brookfield model LVF, spindle 2, Monomers in theinternal phase 60 rpm Melamine acyrlate oligomer (Doresco Approx. 15UV75° C., 1500 cps)/M 50/50 ratio Bisphenol A base epoxy acrylateApprox. 25 (CN120, 2150 cps @ 65° C.)/ M 40/60 ratio Urethanedimethacrylate (CN 1963, Approx. 53 1740 cps@65° C.)/M 50/50 ratioPolybutadiene (Ricon 130, 750 cps)/ Approx. 25 M 50/50 ratio

The above blends can contain up to 5% by weight of DPC activator or CHPinitiator. HDDMA is hexanediol dimethacrylate. THFA istetrahydrofurfuryl methacrylate.

CN polymers and Ricon™ are trademarks of Sartomer (Exton, Pa.). Doresco™is a trademark of Lubrizol (Wickliffe, Ohio). CHP is cumenehydroperoxide; DPC is diphenyl carbazone; CN120 is bisphenol epoxyacrylate.

As used herein, “Mw” means molecular weight average, unless otherwisenoted to the contrary.

Although the flooring system has been described with reference tomultiple floor boards, it is considered within the invention to use thedry preglue system as described herein on any surface of a molding, suchtransition moldings, end moldings, T-moldings, carpet reducers, hardsurface reducers, quarter round moldings, wall base moldings or shoemoldings, as described, for example, in U.S. Pat. No. 6,8660,074, hereinincorporated by reference in its entirety.

1. A surface element, having at least one of a tongue and a groove, comprising: a dry glue disposed on at least one surface of the flooring element, wherein, when activated, said dry glue exhibits a creep strength of between 1 and 50 kN/m, when measured with a gap less than 0.1 mm and a pull rate of 0.02 mm/min.
 2. The surface element of claim 1, wherein the dry glue is a preglue.
 3. The surface element of claim 1 or 2, wherein, when activated, said dry glue exhibits a creep strength of between 7 and 20 kN/m, when measured with a gap less than 0.1 mm and a pull rate of 0.02 mm/min.
 4. The surface element of any of the preceding claims, wherein said dry glue when activated, further exhibits at least one property selected from the group consisting of: tensile strength of 7-20 kN/m when measured with a gap less than 0.1 mm and a pull rate of 2 mm/min; storage stability of at least one year; low initial tack value; and set time of at least 45 minutes.
 5. The surface element of any of the preceding claims, wherein said dry glue when activated, further exhibits each of: a tensile strength of 7-20 kN/m when measured with a gap less than 0.1 mm and a pull rate of 2 mm/min; a storage stability of at least one year; a low initial tack value; and a set time of at least 45 minutes.
 6. The surface element of any of the preceding claims, wherein said dry glue is positioned on said at least one of a tongue and a groove.
 7. The surface element of any of the preceding claims, wherein said dry glue comprises at least one component selected from the group consisting of: a monomer; an initiator; an activator; and a catalyst.
 8. The surface element of claim 7, wherein said at least one of said at least one component is encapsulated.
 9. The surface element of claim 7 or 8, wherein said at least one component is said monomer.
 10. The surface element of any of claims 6-9, wherein said dry glue further comprises a second component selected from the group consisting of: a monomer; an initiator; an activator; and a catalyst, wherein said second component is not encapsulated with said first component.
 11. The surface element of claim 10, wherein said second component is encapsulated.
 12. The surface element of any of claims 1-11, wherein the surface element is a flooring element, and comprises: a core material; a decorative surface on the core material, and a wear layer disposed on the decorative surface.
 13. A surface system comprising: a plurality of surface elements according to any of the preceding claims, wherein at least one of said plurality of flooring elements comprises a tongue and at least one of said plurality of flooring elements comprises a groove.
 14. The surface system of claim 13, wherein said dry glue comprises at least two components selected from the group consisting of: a monomer; an initiator; an activator; and a catalyst, wherein at least one component is present on said tongue and at least one component is present in said groove.
 15. The surface system of claim 14, wherein said at least one component on said tongue is different than said at least one component in said groove.
 16. The surface system of claim 14 or 15, wherein at least one of said components is encapsulated.
 17. The surface system of claim 16, wherein said encapsulated component is said monomer.
 18. The surface system of claim 15, wherein said encapsulated monomer is present on one of said tongue and said groove, and at least one selected from the group consisting of an initiator; an activator; and a catalyst is present on the other of said tongue and said groove.
 19. The surface system of any of claims 11-18, wherein at least one of said tongue and said groove comprise locking elements.
 20. A method of forming a substantially planar surface comprising: providing a first surface element of any of claims 1-12; activating said dry glue; and joining said surface element with a second element.
 21. The method of claim 20, wherein the dry glue further exhibits at least one property selected from the group consisting of: tensile strength of 7-20 kN/m when measured with a gap less than 0.1 mm and a pull rate of 2 mm/min; storage stability of at least one year; low initial tack value; and set time of at least 45 minutes.
 22. The method of claim 21, wherein said second surface element is a surface element of any of the preceding claims.
 23. The method of claim 20 or 21, wherein said first surface element comprises a tongue and said second surface element comprises a groove, wherein at least first component of said preglue is present on at least one of said tongue and said groove.
 24. The method of any of claims 20-23, wherein said activating comprises mating said tongue and said groove.
 25. A method of forming a substantially planar flooring system comprising: providing a first flooring element having a preglue on at least one surface of said first flooring element thereon, wherein the preglue exhibits a creep strength of between 1 and 50 kN/m, when measured with a gap less than 0.1 mm and a pull rate of 0.02 mm/min; activating the preglue; and joining the first flooring element with a second flooring element.
 26. The method of claim 25, wherein the preglue exhibits a creep strength of between 7 and 20 kN/m, when measured with a gap less than 0.1 mm and a pull rate of 0.02 mm/min
 27. The method of claim 25 or 26, wherein the preglue further exhibits at least one property selected from the group consisting of: tensile strength of 7-20 kN/m when measured with a gap less than 0 1 mm and a pull rate of 2 mm/min; storage stability of at least one year; low initial tack value; and set time of at least 45 minutes.
 28. The method of any of claims 25-27, wherein said activating comprises rupturing microbaloons containing at least one component of the preglue.
 29. The method of any of claims 25-28, wherein said activating comprises mating a tongue-and-groove system of the first and second flooring elements.
 30. The method of any of claims 25-29, wherein said activating comprises contacting a first component of the preglue, the first component positioned on the first flooring element, with a second component of the preglue, the second component positioned on the second flooring element. 